Adolescent MDMA use has increased dramatically since 1998, although little is known regarding the clinical impairments or service needs of MDMA-abusing youth. The proposed R03 includes a longitudinal evaluation of the nature and persistence of cognitive and psychiatric impairments in young MDMA abusers. Pilot findings indicate that MDMA abuse is endemic among youth residing at the proposed project site. All residents complete lengthy rehabilitation stays; thus, the proposed study site affords a unique opportunity to study the nature and course of neuropsychiatric dysfunction in youth at risk for the development of MDMA-related functional impairments. Specific aims of the proposed investigation are to describe differences among heavy, moderate, and experimental adolescent MDMA users and nonusers with regard to cognitive and psychiatric dysfunction and evaluate whether heavy MDMA users demonstrate less reversal of these impairments than lighter users or nonusers between admission to the facility and 6-months follow-up. The proposed R03 also incorporates a case-control study comparing the cognitive and psychiatric functioning of all identified heavy MDMA users and matched MDMA-negative, polydrug-using controls. High-resolution MR scans will be collected and analyzed via high-dimensional brain mapping to compare hippocampal volume and shape in a subset of 15 heavy MDMA users and 15 matched controls. Case-control findings will provide feasibility data for a larger study evaluating MDMA-induced changes to brain structures, which may form the neurobiological basis for observed dysfunction. All youth (N equal to about 168) admitted to the state's largest residential facility for juvenile offenders over 14 months will be recruited and will complete neuropsychological tests and structured psychiatric interviews at admission to the facility and 6 months later. Project findings will provide critical preliminary data describing neuropsychiatric impairments in adolescent MDMA abusers and will serve as the basis for a larger and longer-term study of young MDMA abusers.